In the prior art, a part of this shape made of composite material with continuous fiber reinforcement in a thermoplastic matrix could be obtained by stamping a consolidated thermoplastic blank. In that prior art, described for example in the document FR-A-2 922 276, a stack of pre-impregnated plies is compacted and consolidated in order to make up a plate. Nested parts are then trimmed out of the plate to make blanks, which blanks are then stamped by a punch-and-die device at a temperature close to or above the melting temperature of the matrix. A composite blank with fiber reinforcement is stamped without changing the thickness of the blank, the material of which cannot undergo plastic deformation. Thus, during the stamping operation, said blank is deconsolidated during heating so as to allow the inter-laminar slipping of the plies during forming, then compacted once again between the die and punch following stamping before it is consolidated once again and finally trimmed to eliminate the edges. FIG. 1 relating to the prior art schematically illustrates the direction of the fibers during certain steps of the method. Thus, in FIG. 1A, at the end of the consolidation of the composite plate (100), the plate in this embodiment comprises continuous fibers (110, 120), that is to say extending between two edges of said plate, oriented along angles at 0° (120) and 45° (110). Before stamping, in FIG. 1B, a plurality of blanks (130) is trimmed in that plate (100) for example by means of an abrasive water jet. The need to follow the direction of fibers imposes the direction of the blanks in the plate (100), which limits the possibilities of nesting parts and leads to large scrap rate. Besides, during that trimming stage, particularly when the blank (130) is curved, it is not possible to follow the nominal direction of fibers in all locations of the blank. Thus, the subsequent stamping operation generates tensions in the fibers, depending on their direction in relation to the forming direction. In the prior art, the use of a blank made out of a compacted and consolidated plate is indispensable for implementing the hot stamping method. That is because in order to achieve the inter-laminar slipping of the plies during forming, it is necessary for the heating temperature of the blank to be even, both at the surface and in the thickness. The presence of an air knife in the stratification, even over a short distance, creates a lack of heating, which is reflected in a point of fixation between the relevant plies, locally opposing the inter-laminar slipping and generating stresses in the fibers. Further, that air knife collects the products of the gas released when the blank is heated, thus creating porosity. To avoid those defects, the condition of the material of the consolidated plates (100) is systematically inspected in the prior art using ultrasound, before the blanks for stamping are trimmed. The document “Manufacturing processes for advanced composites”, Chapter 10: pages 379-387, CAMPBELL F. C. ED., ELSEVIER ADVANCED TECHNOLOGY, Jan. 1, 2004 describes the techniques for stamping thermoplastic composite materials with continuous fibers. These operations of consolidation, repeat consolidation and systematic inspection have an adverse effect on the cost of parts and the productivity of the implemented method, while the faulty orientation of the fibers in the part leads to reduced mechanical properties of said part, and for aeronautics applications, extra mass for equivalent mechanical performance, or even does not allow the use of such parts in certain applications. For example, aircraft fuselage frames consist in L or U-shaped sections that are bent along a curvature radius above 2 meters for a medium-body aircraft. These frames are advantageously made up of a composite material with fiber reinforcement that is lighter than metallic materials, with equivalent mechanical strength. However, for such structural parts to be able to withstand the many mechanical stresses to which they may be subjected in normal service and in exceptional conditions, particularly in terms of buckling, these parts must be made with tight tolerances in respect of the direction of the reinforcing fibers in relation to the neutral line of the part, which direction tolerance is generally less than 1°. Thus, the method of the prior art does not make it possible to make a composite part with continuous reinforcement and a thermoplastic matrix meeting those tolerances.
The document WO 02/09935 describes a method that implements the stamping of a composite blank with a pre-consolidated thermoplastic matrix. The stamping method considered in that document is carried out by squeezing the edges of the blank during stamping, and so it is only adaptable for blanks reinforced with discontinuous fibers, with no control of inter-laminar slipping during the stamping operation, and with a variation of the thickness of said blank.